i use this by putting the mage as focus and using it whenever i see him sheeping me, helps alot and is very useful since you dont have to change your current target to get the sw:death off. as far as the modifier in the macro, it doesnt have to be shift, whatever works for you. thats just what i use. for example, 5 is my sw:death. i can press 5 anytime and it does what normally sw:death does to my current target. now when i press Shift+5, it will sw:death my focus target.

also what i like to do is combine my battlemaster trinket with my healthstone, for a nice hp boost when needed, its an easy macro and goes like this:

/use battlemaster's perserverance
/use master healthstone

hope these prove to be useful to whoever uses them just as useful as they are to me.

PS. a good shadow priest macro for mind flay

#show tooltip Mind Flay
/cast [nochanneling:Mind Flay] Mind Flay.

what this does is lets u spam mind flay w/o reseting it during a channel. allowing u to conserver your mana.